1. Technical Field
The present invention relates to sealant formulations useful for sealing punctures in pressurized items. The present invention is particularly useful for sealant formulations for relatively high pressure tubeless tires. The present invention also resides in a tubeless tire, especially a high pressure tubeless tire, comprising the sealant of the present invention.
2. Description of the Prior Art
U.S. Pat. No. 3,981,342 discloses a puncture sealing composition for a pneumatic tubeless tire. The composition comprises a high molecular weight elastomer, a low molecular weight liquid elastomer, and a cross-linking agent to partially crosslink the elastomers. The low molecular weight liquid elastomer used in the examples is a heat depolymerized natural rubber marketed by Hardman Company under the trademark DPR-400. Samples of DPR-400 were analyzed, for purposes of comparison in the present invention, and were found to contain relatively large amounts of iron, some samples ranging by way of example from 25 to 2,500 parts per million (ppm) iron. The patent also mentions that other low molecular weight liquid elastomers can be used, such as cis-polyisoprene polymerized to a low molecular weight, liquid polybutadiene, liquid polybutene, liquid EPDM, and liquid butyl rubber. However, no trademarked examples are given of these other low molecular weight liquid elastomers, or of their use.
U.S. Pat. No. 4,064,922 also discloses a puncture sealing composition for a pneumatic tubeless tire. The composition comprises a high molecular weight elastomer, a low molecular weight liquid elastomer, and a cross-linking agent to partially crosslink the elastomers. The low molecular weight liquid elastomer used in mos of the Examples is the same heat depolymerized natural rubber marketed by Hardman Company under the trademark DPR-400. A preferred cross-linking agent is a titanate ester. The patent also contains Examples in which the low molecular weight liquid elastomer is Butyl LM 430 marketed by Enjay. This is a liquid polyisobutylene having an average molecular weight of 32,000. The composition has low unsaturation (about 4 mole percent).
U.S. Pat. No. 4,913,209 discloses a puncture sealing composition for a pneumatic tubeless tire. The composition comprises a high molecular weight elastomer, a low molecular weight liquid elastomer, and a cross-linking agent to partially crosslink the elastomers. The low molecular weight liquid elastomer disclosed in the examples is the depolymerized natural rubber marketed by Hardman Company under the trademark DPR-400. The sealant is a laminate sealant in that it is applied to a web for a tire, prior to curing, and then is cured with the tire in the tire curing process. A preferred cross-linking agent is a quinoid curing system, such as p-quinone dioxime, or an organic peroxide or hydroperoxide, such as dicumylperoxide.